U.S. patent number 5,006,862 [Application Number 07/429,251] was granted by the patent office on 1991-04-09 for fixation of reactive dyes to paper by ink-jet printing.
This patent grant is currently assigned to Hewlett-Packard Company. Invention is credited to Raymond J. Adamic.
United States Patent |
5,006,862 |
Adamic |
April 9, 1991 |
Fixation of reactive dyes to paper by ink-jet printing
Abstract
The water-fastness and smear resistance of prints from inks in
which a reactive moiety is attached to a chromophore are improved
if the prints are treated with a strong base solution. Preferably,
the paper is first treated with the base solution and then printed
with the ink.
Inventors: |
Adamic; Raymond J. (Corvallis,
OR) |
Assignee: |
Hewlett-Packard Company (Palo
Alto, CA)
|
Family
ID: |
23702456 |
Appl.
No.: |
07/429,251 |
Filed: |
October 27, 1989 |
Current U.S.
Class: |
347/101;
106/31.47; 106/31.49; 106/31.58; 346/25; 346/96; 347/100; 347/96;
8/543 |
Current CPC
Class: |
B41M
7/00 (20130101) |
Current International
Class: |
B41M
7/00 (20060101); B41J 002/01 () |
Field of
Search: |
;346/1.1,75,140 ;8/543
;106/22 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Hartary; Joseph W.
Claims
What is claimed is:
1. A process for printing reactive dyes on a medium,
comprising:
(a) printing said medium with an ink-jet ink comprising
(1) about 1 to 10% of a reactive dye having a reactive moiety,
(2) about 5 to 15% of an organic solvent selected from the group
consisting of 2-pyrrolidone, N-methyl pyrrolidone, and glycols,
and
(3) about 75 to 94% water, said ink having a pH adjusted to about 5
to 9; and
(b) treating said medium with a basic alcoholic solution containing
from about 90% to about 100% alcohol, by weight, of an alcohol
having from 1 to 6 carbon atoms, said alcoholic solution having a
pH from about 10 to about 13.
2. The process of claim 1 wherein the medium is first printed and
then treated.
3. The process of claim 1 wherein the medium is first treated and
then printed.
4. The process of claim 1 wherein the reactive dye has a
monochlorotriazine group as the reactive moiety.
5. The process of claim 1 wherein the reactive dye has a
dichlorotriazine group as the reactive moiety.
6. The process of claim 1 wherein the reactive dye has a vinyl
sulfone group as the reactive moiety.
7. The process of claim 1 wherein the medium is a cellulosic
material.
8. The process of claim 7 wherein the medium is a cellulosic
paper.
9. The process of claim 1 wherein the basic solution is 0.05M to 1M
NaOH.
10. The process of claim 1 wherein the alcohol is methyl, ethyl,
propyl, or isopropyl alcohol.
11. The process of claim 10 wherein the alcohol is methyl
alcohol.
12. The process of claim 1 wherein said ink has the formulation
Description
TECHNICAL FIELD
This invention is concerned with the use of reactive dyes in
ink-jet printing. More particularly, it involves the fixation of
such dyes to paper.
BACKGROUND ART
Ink-jet printers generally use inks that contain water-soluble
dyes. Such dyes are often not very smear resistant or water
resistant when printed on paper.
The use of colored inks in ink-jet printing is known; for example,
U.S. Pat. No. 4,382,262 and U.S. Pat. No. 4,360,548 disclose such
systems. These patents, however, do not disclose or suggest forming
smear-resistant inks on a substrate, such as paper.
Hackleman and Pawlowski addressed this problem in U.S. Pat. No.
4,694,302. In their method, a polymer is formed on the substrate
from two reactive components; one component may be in the ink and
the other may be in the substrate or it may be applied from a
second reservoir. The resultant polymer binds the dye. In one
example, sebacyl chloride was include in the ink; when it was
deposited on a cellulose-containing substrate, it formed a
cellulosic polymer. In another example, the ink contained
carboxymethyl cellulose, and a second solution contained 2%
AlCl.sub.3. When these solutions were deposited on a substrate,
they reacted to form an insoluble salt of the carboxymethyl
cellulose polymer.
A method for determining the degree of reactive dye bonding to
cellulose is summarized in Dialogue abstract 268024 50-08024. Dyed
chromatographic paper is boiled for 5 minutes in distilled water
followed by colorimetric determination of the desorbed dye. The
summary also notes that the test can be used for the determination
of the effects of alkali concentration on the bonding degree.
DISCLOSURE OF THE INVENTION
The method of the present invention uses commercially available
reactive dyes as a viable component in ink-jet printing. The
reactive dyes have a reactive moiety attached to the chromophore
and are capable of forming a covalent bond to a paper substrate. A
basic solution of high pH is employed to fix the dye to the paper.
The ink containing the reactive dye can be printed before or after
the basic solution is applied, but better results are obtained when
it is applied afterwards.
DETAILED DESCRIPTION OF THE INVENTION
A reactive dye, such as one having a mono- or dichlo-rotriazine
group or a vinyl sulfone group as the reactive moiety is made into
an ink corresponding to the following formulation:
______________________________________ reactive dye about 1 to 10%
organic solvent about 5 to 15% water about 75 to 94% pH adjusted to
about 5 to 9. ______________________________________
All percentages herein are by weight.
The organic solvents preferably are 2-pyrrolidone,
N-methylpyrrolidone, etc. Glycols and alcohols may be used,
especially as a cosolvent with one of the lactams already
named.
The pH of the inks is best kept from about 5 to about 9 because of
stability considerations. The optimal pH is dependent upon the
particular class of reactive moiety in the dye. The more reactive
dyes, such as dichlorotriazinyl dyes require milder conditions. In
general, the pH should be fairly neutral.
A buffer is used to keep the pH constant so that the reactive dye
will not degrade under too acidic or too basic conditions. Buffers
which have a buffering capacity in the pH range indicated may
employed. If the pH strays beyond this range, it will accelerate
the decomposition of the reactive dye; the degree is dependent on
the reactivity of the dye.
Preferred ink compositions of this invention correspond to the
following formulation, by weight:
______________________________________ reactive dye about 2 to 4%
2-pyrrolidone about 8 to 12% water about 84 to 90% pH adjusted to
about 5 to 8. ______________________________________
In general, the pH of the inks should be fairly neutral, since
reactive dyes tend to react with a wide range of materials,
including the hydroxyl ion in water. On the other hand, if the ink
is too acidic, it is likely to cleave the reactive moiety from the
dye molecule.
The inks of this invention generally will contain a biocide. If
crusting is a problem, then a humectant can be added.
After solubilization, the ink is printed on paper from an ink-jet
cartridge with a thermal ink-jet printer. A second ink-jet
cartridge containing a strong base solution, with or without
alcohol, is used to fix the ink to the paper. The pH of the base
solution should be greater than 10, and the base may be compounds
such as NaOH, KOH, LiOH, or amines. Solutions as strong as 1M may
be used, although solutions of about 0.1M to about 0.5M NaOH in
water are preferred.
Preferably, the base solution will have a pH from about 10 to about
13 and will be applied first, followed by printing with the ink
solution. The base breaks up hydrogen bonding in the paper. It
causes the paper to swell which helps absorption of the dye. After
abstraction of the proton by the base, the cellulosic fiber becomes
nucleophilic and is capable of attacking the reactive group of the
dye and form a covalent bond. For example, if the paper has been
treated with NaOH solution and then printed with a chlorotriazine
dye, sodium chloride splits off and leaves the rest of the dye
bonded to the cellulose.
If the base solution includes from about 90% to about 100% by
weight of an alcohol corresponding to the formula ROH, wherein R is
an alkyl radical which has from 1 to about 6 carbon atoms, then the
print will dry faster and the amount of wrinkling of the paper is
reduced. Typical alcohols are methyl, ethyl, isopropyl, and n-butyl
alcohol.
The best method to apply the base and the ink is by dot-on-dot
printing. In this method, one applies a dot of base followed by a
dot of ink. This ensures that full coverage of base will bind the
dye to the paper and minimize print quality defects. The base may
be applied after the ink has been laid down without significantly
reducing the quality of the print or its fastness, but the result
appears to be not quite in the same par as that obtained with
printing after the base has been laid down. In either event, the
printed paper is allowed to dry.
The invention is particularly useful for printing pure cellulosic
papers, such as chromatography paper, or papers which contain
cotton content, such as 50% or 25% cotton bond.
The degree of water-fastness can be determined by submerging a
sample in water for five minutes and determining the amount of ink
which is transferred to the white portion of the paper. Smear
resistance is determined by measuring the amount of dye transferred
across the white portion of the paper using a conventional
highlighter pen. Optical density is measured, using a
densitometer.
The present invention provides prints that have high smear
resistance and water fastness. As indicated in the following
tables, zero smear resistance is obtained as well as low .DELTA.L
values. L is a measure of the darkness of the sample; the higher
the L value, the lighter the print. A smaller .DELTA.L value after
washing between two samples with similar initial L values indicates
less dye transferred or lost.
In the claimed process, the dye is bonded to the paper by the base.
This is indicated by the following:
1. The hydrolyzed dye does not show the same behavior as the
unhydrolyzed dye.
2. The reactive site on the dye is disabled.
3. Water-fast tests done at 100.degree. C. for 10 minutes instead
of the normal five minute test at room temperature show only a one
unit increase in .DELTA.L.
4. Water based dyestuffs which do not contain reactive moieties
show no improvement when used with the base treatment, and solvent
induced effects, for example, the effect of a solvent such as
2-pyrrolidone, does not help much in aiding water-fastness when
reactive dyes are present in the ink.
5. Drytime is less than 10 seconds with the base treatment, and
this is considerably less than drytime without the base
treatment.
When a two-pen design is used, the stability of the ink formulation
is increased, because the pH of the ink formulation can be set near
neutral where stability of the reactive dye is greatest. The
invention also permits the use of other curing agents that are
suitable for fixation and can possibly be included in the pen.
Curing agents may be amines such as ammonia (from about 0.1 to
about 0.5M), propylamine, or ethylamine; about 0.1 to about 1M
sodium methoxide or sodium ethoxide; sodium bicarbonate or sodium
hydroxide. In addition, a two-pen design provides greater
versatility in printing; the ink and the alkali may be incorporated
into a single compartmentalized unit or two separate units may be
used.
EXAMPLES
EXAMPLE 1
Ink formulations containing 2% (A), and 4% (B) Procion MX-CWA (a
dichloro-s-triazinylamino dye), and 10% 2-pyrrolidone in water were
printed on 100% cellulosic paper from a ink-jet printer. Papers had
first been treated in the same alphanumeric pattern with 0.1M NaOH
and 0.5M NaOH solutions, respectively.
______________________________________ Formulation Treatment L
.DELTA.L ______________________________________ A1 (pHi = 9.7)
untreated 58 22 A1 0.1M NaOH 58 5.3 A1 0.1M NaOH (boiled) 58 7.4
(boiled) = 10 min. in distilled water A1 0.5M NaOH 56 6.4 A2 (pHi =
9.8) untreated 58 20.7 A2 0.1M NaOH 57 6.7 A2 0.5M NaOH 56 6.2 A3
(pHi = 6-7) untreated 59 21.3 A3 0.1M NaOH 54 7.7 A3 0.5M NaOH 56
4.6 A4 (pHi = 6.9) untreated 57 25.1 A4 0.1M NaOH/MeOH 57 4.0 A4
0.5M NaOH/MeOH 57 4.5 B (pHi = 7.1) untreated 49 28.1 BP 0.1M
NaOH/MeOH 49 4.3 BP 0.5M NaOH/MeOH 49 4.6
______________________________________ pHi is initial pH; MeOH is
100% methyl alcohol.
EXAMPLE 2
Formulations A3, A4, and B were printed on 50% cotton bond paper.
Specimens were treated as indicated below, and water-fastness
tested with the following results:
______________________________________ Formulation Treatment L
.DELTA.L ______________________________________ A3 untreated 49
24.5 A3 0.1M NaOH 54 9.3 A3 0.5M NaOH 57 5.9 A4 untreated 49 26.2
A4 0.1M NaOH/MeOH 59 6.2 A4 0.5M NaOH/MeOH 58 4.7 B untreated 40
34.5 BP 0.1M NaOH/MeOH 52 12.3 BP 0.5M NaOH/MeOH 52 4.9
______________________________________
EXAMPLE 3
Formulation A5, which duplicated formulation A4, was printed on 25%
cotton bond paper; the paper had been treated as indicated below.
The specimens were tested for water-fastness.
______________________________________ Formulation Treatment L
.DELTA.L ______________________________________ A5 untreated 47
22.2 A5 0.1M NaOH/MeOH 61 4.4 A5 0.5M NaOH/MeOH 60 3.6
______________________________________
EXAMPLE 4
4% Procion Red MX-58 (a dichloro-s-triazinylamino dye) and 10%
2-pyrrolidone were dissolved water and the pH adjusted to 7.4 with
aqueous NaOH. Specimens of paper were printed with the formulation
after pretreatment with 0.5M NaOH/100% MeOH. The specimens were
then tested as indicated.
______________________________________ Smear Dye Transfer
Resistance Paper (mOD) 2-pass Cellulose Gilbert Gilbert (mOD) L
.DELTA.L L .DELTA.L OD Dye Gilbert
______________________________________ 55.3 4.1 57.8 4.4 0.63 30 0
When the paper was printed first and then the base was applied, the
results were as follows: xx xx 52.0 5.6 0.76 111 22.4 Untreated
paper gave the following results: xx xx xx xx 0.76 351 140
______________________________________
EXAMPLE 5
4% Procion Red MX-8B, 10% 2-pyrrolidone, in water with pH adjusted
to 6.7 gave the following results on Gilbert Bond:
______________________________________ Smear Dye Transfer
Resistance L .DELTA.L (mOD) 2 pass (mOD)
______________________________________ After treatment with 0.5M
NaOH/100% MeOH: 54.3 4.3 oD = 0.72 27 O When the ink was applied
first: 47.84 5.1 oD = 0.87 124 35.2 When ink was applied first,
followed by two treatments with base: xx xx oD = 0.89 86 33.2
______________________________________
EXAMPLE 6
1% Cibacron Black (a monochloro-s-triazinylamino dye) and 10%
2-pyrrolidone water dissolved in water and the pH adjusted to 6.91.
When printed on Gilbert Bond that had first been treated with 0.5M
NaOH/100% MeOH, a two pass smear resistance test gave an mOD
(millioptical) density as measured by densitometer of 16.2 on 50%
cotton bond.
INDUSTRIAL APPLICABILITY
The present invention is useful in printing reactive dyes from
ink-jet printers. It is particularly useful in printing papers
containing cellulosic fibers.
* * * * *